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Electric-Field Strength
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
In this section, measurement techniques for extremely low frequency (ELF, 3 Hz to 3 kHz) and ultralow frequency (ULF, below 3 Hz) electric fields are considered. Natural ELF fields are produced by thunderstorms, and natural ULF fields are produced by micropulsations in the Earth’s magnetic field [7]. Geophysicists make use of these natural fields in the magnetotelluric method for remote sensing of the Earth’s crust [8]. AC power lines are dominant sources of fields at 50 or 60 Hz and their harmonics.
DEMETER Satellite and Detection of Earthquake Signals
Published in Ramesh P. Singh, Darius Bartlett, Natural Hazards, 2018
The emissions can propagate up to the ionosphere, and observations made with low-altitude satellites have shown increases of ULF, ELF and VLF waves above seismic regions. The first ionospheric observations of EM emissions onboard satellites have been presented in Gokhberg et al. (1982) and Larkina et al. (1983). Larkina et al. (1983) reported case studies when the INTERKOSMOS-19 satellite passed over epicentres of EQs. The following observations were made by Larkina et al. (1983):
Geomagnetic Field Effects on Living Systems
Published in Shoogo Ueno, Tsukasa Shigemitsu, Bioelectromagnetism, 2022
A recent long-term study examined the relationships between the solar and magnetic factors and the time course and lags of autonomic nervous system responses to changes in solar and geomagnetic activity (Alabdulgader et al., 2018). In this study, the inter-beat-interval (IBI), Total power, low-frequency (LF) and high-frequency (HF) powers, the LF/HF ratio, and very low-frequency (VLF) power were used as parameters of HRV measures (Alabdulgader et al., 2018; Table 6.2). Here, the power spectral density values reflect the area under the curve within the specific bandwidth of the spectrum. The interactions between autonomic neural activity, BP, respiration, and higher-level control centers in the brain produce both short- and longer-term rhythms in HRV measurements (McCraty and Shafer, 2015). The heart rhythm fluctuations are separated into three primary frequency bands: HF, LF, and VLF (Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology, 1996). The “ultralow-frequency (ULF)” is generally described as geomagnetic activity <3.5 Hz. The GMF-line resonances are the most common source of ULF wave energy measured on the ground and exhibit the largest wave amplitudes compared to other oscillations that occur in the magnetosphere (Southwood, 1974). IBI is the time in milliseconds between consecutive heartbeats. Total power is a measure of all the HRV bands combined, and therefore is a measure of the overall HRV from all physiological sources, although it is highly affected by the VLF power. Space weather and environmental measures were obtained from three sources, comprising nine measures. The solar wind speed, Kp index, Ap index, number of sunspots, F10.7 index, and the geomagnetic polar cap index (PCN) were downloaded from NASA Goddard Space Flight Center’s Space Physics Data Facility as part of the Omni 2 data set (Alabdulgader et al., 2018). Here, the F10.7 index is a “solar radio flux” at 10.7 cm (2,800 MHz) (Tapping, 1987). That is a measure of the solar flux unit (sfu) frequency at a wavelength of 10.7 cm, near the peak of the observed solar radio emission. F10.7 is often expressed in sfu (1 sfu = 10−22 W/m2 Hz). It represents a measure of diffuse, nonradiative coronal plasma heating. It is an excellent indicator of overall solar activity levels and correlates well with solar UV emissions. GCR counts were downloaded from Finland’s University of Oulu’s Sodankyla Geophysical Observatory’s website (Alabdulgader et al., 2018). Power in the time-varying MF in two frequency bands, SR Power, 3.5–36 Hz and ULF power, 2 mHz to 3.5 Hz were obtained from a recording site located in Boulder Creek, California (Alabdulgader et al., 2018).
DWT-based methodology for detection of seismic precursors on electric field signals in Mexico
Published in Geomatics, Natural Hazards and Risk, 2018
O. Chavez, J. R. Millan-Almaraz, J. Rodríguez-Reséndiz, J. P. Amezquita-Sanchez, M. Valtierra-Rodriguez, J. A. L. Cruz-Abeyro
There are many studies that report relations between earthquakes and other physical phenomena. These phenomena mainly include disturbances such as electromagnetic (EM) anomalies associated with the earthquakes. They often encompass a large frequency range, which comes from quasi-dc to high frequencies, being ultra-low-frequency (ULF) range (0.001-1 Hz) the most promising, because it has been associated with anomalies produced in Earth's EM field before large earthquakes (Johnston 1997; Kushwah et al. 2009). Other physical anomalies related to pre-earthquake disturbances such as an increment in radon emanation from the ground to the atmosphere, water chemistry alterations, haze production and induced changes in the electric field, among others have been reported (Chen et al. 2004; Pulinets et al. 2003; Pulinets and Boyarchuk 2004; Rishbeth 2006; Freund 2013; Depueva et al. 2007; Liu et al. 2006a; Liu et al. 2006b; Karatay et al. 2010; Le et al. 2011; Namgaladze et al. 2012; Devi et al. 2014; Akhoondzadeh 2015; Heki and Enomoto 2015).
Quantitative effects of cyclotron resonance on the coupling of ULF with VLF and langmuir waves
Published in Waves in Random and Complex Media, 2021
Asif Shah, Shahzad Mahmood, Saeed Ur Rehman
The ULF waves are hydromagnetic in nature and occupy a vast band 1 mHz–10 Hz ([1] and references therein). These waves have been classified into two categories, continuous pulsations (Pc) and irregular pulsations (Pi). In Pc there are five sub-bands, Pc1 (oscillation periods fall in the range of 0.5–5 seconds), Pc2 (5–10 seconds), Pc3 (10–45 seconds), Pc4 (45–150 seconds), Pc5 (150–600 seconds). However, the Pi oscillations have only two sub-bands, Pi1 (1-40 seconds), and Pi2 (40–150 seconds) [1,2]. The VLF waves are electromagnetic oscillations at 3–30 kHz [3]. The frequencies of Langmuir oscillations are strongly dependent on the plasma frequency and electron thermal speed [4].